I have a 2000 S40, that I have owned since 2001. I have always gotten mileage that ran between 22-27 mpg depending on city or highway. In the past couple of weeks, I have noticed a serious decline. I am now getting only around 16-17 mpg if I am lucky.

I have always put in premium fuel and I every time I fuel up, I re-set my trip mileage. For the first couple of years, I meticulously tracked my mileage/gas efficiency with every single tank of gas but stopped when it stayed pretty constant. I seem to recall, when I was doing research way back when on whether to buy this car or not, I saw some discussion about this problem and possible causes. I have searched and nothing came up. Anyone else having this "issue"? I have about 80,000 miles and all service/tune-up's have been performed on schedule.

To note (and possibly releated) I have *twice* had to have the Engine Coolant Temperature (ECT) sensor and thermostat replaced. Last time was Dec. 2005. The car would suddenly surge in RPM's to 4k-5k as if I was flooring it. I was a stoplight at a busy intersection of a highway, and if I hadn't had my foot firmly on the brake I would have shot forward, leading to my untimely demise, or at the minimum, very serious injuries. It was pretty scary. Putting it into neutral didn't have any effect. I had to shut off the engine and restart it. It took about 3-4 times of restarting the car before it would start with normal low RPM's. When I took it to the dealer, they said a faulty ECT sensor was flooding the car with gas. They replaced the sensor and thermostat kit (about $200 for everything) and the problem went away.

Also, noteworthy, the "check engine" light did NOT come on during the intersection incident. The next day, on my way home, it happened again on the highway shooting me down the highway, or then it would stop as if I was running out of gas, you know, that horrible stutter/puttering when its on its last fumes. That time the "check engine" light DID then come on. I ended up having to have it towed from the side of the highway to the dealer, which is when said prognosis of ECT was made.

I called the dealer the other day asking about my serious decrease in mileage and his response was "Is the check engine light on?" It is not. He then replied "Well, you don't have a problem. Those lights are very sensitive and if anything was wrong, or it was running rich, it would come on." Right. Thanks.

Basically, it was dismissed. Anyone have any ideas or suggestions?

Thanks!

 

The fuel pump might be going bad.

 

Thanks, I will have that checked out. Would this be something that would not registar on the all-knowing, all-seeing oracle of the "Check Engine" light?

 

If the pump goes bad it will NOT set codes.

 

Greetings to all,

New user here, joined specifically to find information about a recent problem I'm having...a sudden and marked DECREASE in fuel economy with my 2000 Volvo V40 1.9T. I bought the car 3 months ago from a doctor who babied this vehicle. It has been religiously maintained and only now has about 52,000 miles on the odometer.

I am one of the 'neruotic' types that tracks and records my mileage with every fill up. I noticed that I was getting, consistently, between 20-21 mpg with mostly local driving, and using 89-91 octane gas. Now, as of the past 2 weeks, I'm lucky if I get 17 mpg (I'm actually seeing figures between 15 and 16).

Upon reading the preceding posts in the thread for this topic, I'm beginning to wonder if my fuel pump could be getting ready to die as it seems to be pretty loud to my ears. So much so that I asked my mechanic (a Volvo specialist of many years) if the fuel pump was voicing it's intent to retire soon. He said that the high-pitched whine I was hearing was normal for this fuel pump...as for the high-pitched whine coming from my girlfriend, well there was no advice he could offer there other than an understanding look, followed by a subtle shrug of the shoulders...

Anyway...I haven't gotten into the vehicles history too much...i.e. I don't know if/when the car was ever tuned up (spark plugs, fuel and air filters...etc). I do know that the car runs smoothly and acceleration is adequate (just adequate...not great, just adequate).

I was also wondering if it could be needing an oil change. It's been about 3,000 miles and the oil is showing signs of being dirty, but not that bad compared to what I've seen in other cars. I normally change my oil every 3K miles anyway...although my Volvo mechanic says that every 5K is sufficient (I think I'd rather err on the side of changing it too often, than not often enough).

Any ideas, suggestions or comments would be greatly appreciated...

Thanks,
Mark DiRollo
Norwalk, CT